Current Conditions at Sanborn Field
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Discussion:
Thursday’s rain is expecting to hold off until this evening and overnight into Friday, leaving us with an overcast but dry day. We may see some fog Friday morning, but conditions should clear and dry out throughout the day and overnight. Friday’s clearing sky will let us catch a glimpse of the sun before another round of rain on Saturday. Temperatures are expected to be relatively consistent over the next few days as they sit in the low 50s to upper 40s during the day and low 40s to upper 30s overnight.
-Sallot
Forecasters: Sausen, Sallot, Baker
Date Issued: 12/08/2022 12:48 PM CST
Visible satellite observations show instability over Northern Arkansas. Elevated radar reflectivity over the same area indicates precipitation. RAP analysis shows moisture present over the CWA, but no forcing for necessary for precipitation, which explains the lack of rain so far today. Therefore, the possibility of rain showers Thursday evening into Friday will be the focus of this forecast.
Due to the uncertainty of rain throughout the forecast period, this forecast utilizes output from the HRRR, NAM12, and GFS20. The HRRR shows some precip over the CWA Fri 02Z to 07Z. At 250mb, the GFS shows divergence over the CWA Thurday 15Z and Friday 09Z. Both the GFS and NAM have the subtropical jet positioned over the CWA throughout the forecast period with zonal winds out of the west. The GFS shows more divergence over the CWA on Saturday 09Z in association with a east-moving shortwave trough.
There are scattered vorticity values at 500mb over the CWA on Thursday 00Z through Friday 00Z. A second band of vorticity associated with a shortwave trough passes over on Saturday 09Z to 18Z. The second band coupled with divergence at the 250mb level would provide adequate forcing for active weather.
At 700mb, the GFS shows significantly more moisture present over the CWA from Thursday 00Z through Friday 00Z, however the NAM still shows some moisture present in this time span. The NAM also shows negative omega values for Friday 00Z through 09Z, providing another lifting mechanism for moisture. Both the GFS and the NAM show another round of moisture on Saturday 09Z through 18Z which should provide ample cloud cover over the CWA.
A high pressure system situated near the Gulf of Mexico should bring warm moist air northward through the CWA on Thursday 06Z through Friday 12Z. Moisture transport vectors and resulting high RH values on both models also support this transport. Another round of high RH values will arrive Saturday 09Z into Sunday 00Z.
Surface winds increase to 10 knots out of the east Thursday 18Z but then make a rapid switch out of the west on Friday 15Z as a result of a low pressure system from the north moving eastward. Solenoids present from 00Z until 21Z Friday further indicate advection of warm, moist air into the CWA from the Gulf of Mexico.
GFS model soundings show near saturation from 400mb to the surface until 15Z Thursday, saturdation then progresses from the top down to the surface. K index values reach their maximum at 30, indicating a significant chance for rain showers. CAPE values are minuscule, however, so there is little thunderstorm potential throughout the forecast period. Lingering saturation near the surface displayed on the NAM sounding may also indicate the presence of fog Friday morning. Overall, many conditions are present for precipitation to occur Thursday evening into Friday morning.
-Sausen
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